Canning Food Properly is Vital
Improper canning can lead to food poisoning.
August 14, 2019 | View PDF
Don't invite botulism to your dinner table.
Botulism is a deadly form of food poisoning. The toxin, or poison, causing the illness commonly is associated with improperly processed home-canned vegetables, such as peas, peppers, corn, lima beans, green beans and mushrooms, as well as other low-acid foods that are canned at home, including soups, meats, fish and poultry.
If canned food isn't processed properly, spores of the bacteria Clostridium botulinum aren't killed. Even a taste of contaminated food can make a person sick or worse.
Symptoms of botulism include blurred or double vision, slurred speech, difficulty swallowing, muscle weakness, nausea, vomiting, stomach ache and diarrhea. The symptoms usually start to appear 18 to 36 hours after eating food containing the toxin.
Botulism is treatable if the victim receives prompt medical care. Without treatment, the illness causes paralysis that starts with the head and moves to the arms and legs and can cause death, the Centers for Disease Control and Prevention says.
"We're entering the heart of home canning season, so it's critical to use up-to-date equipment and research-tested methods," says Julie Garden-Robinson, North Dakota State University Extension food and nutrition specialist. "I've noticed that many people are unaware that home-canned tomatoes need to be acidified with lemon juice or citric acid and properly processed to be safe. I've also heard about people following questionable advice found on the internet."
Use Proper Canning Equipment
Besides high-quality ingredients, the proper equipment for safely canning low-acid foods such as vegetables, meat and many mixtures of foods includes a pressure canner and standard canning jars with new two-piece lids.
"If you are tempted to can foods in your oven because you heard about it on Facebook or Pinterest, don't do it," Garden-Robinson cautions. "It's dangerous on many levels, including jar breakage and improper heat penetration for safety.
"You may be seeing late-night infomercials that suggest canning in electric multi-cookers," she adds. "However, the National Center for Home Food Preservation does not support the use of U.S. Department of Agriculture canning processes in these appliances, even if they have 'canning' buttons on the front panels."
Foods such as salsa, which is a mix of acid and low-acid ingredients, need to be acidified properly with lemon juice or vinegar using a tested formula and processed according to current recommendations.
"If you have a favorite salsa recipe that has not been research-tested, it's safest to freeze it rather than can it," Garden-Robinson says. "If you use a commercial salsa mix, follow the directions closely. Do not add extra onions and peppers because those ingredients will affect the acidity and the safety of the canned food."
Prepare Canning Lids Correctly
Garden-Robinson also recommends home canners be sure to follow the manufacturer's directions for preparing the canning lids. Boiling the lids when they are not meant to be boiled can result in jars that unseal in your cupboard.
Food containing the botulism toxin generally doesn't taste or look unusual, although the lids on commercial cans may provide a clue that the food is contaminated. Garden-Robinson recommends throwing away any commercial cans that are swollen or bulging and food from glass jars with bulging lids. You also shouldn't taste food from swollen containers or food that is foamy or smells bad.
But even properly processed canned foods won't last forever. For example, cans and metal lids on glass jars can rust. Remove the metal lids from home-canned foods after the jars have sealed and cooled at least 24 hours before storing them.
Light may cause food in glass jars to change color and lose nutrients. Temperatures above 100 F also can cause food to spoil. The acid in foods such as tomatoes and fruit juices can cause commercial cans to corrode.
Here is some advice for storing canned foods, including home- and commercially canned foods:
- Store canned foods in a cool, clean, dry place where temperatures are below 85 degrees. Temperatures in the 60- to 70-degree range are ideal.
- Use home-canned foods within one year for best quality.
- Store commercially canned low-acid foods (such as green beans and peas) in a cupboard for up to five years, according to the USDA.
- Use high-acid commercially canned foods (such as tomato-based products) within 12 to 18 months. Foods stored longer will be safe to eat if they show no signs of spoilage and the cans don't appear to be damaged, but the food's color, flavor and nutritive value may have deteriorated.
Visit NDSU Extension's newly updated food preservation website at https://www.ag.ndsu.edu/food for the latest guidelines on canning, freezing, drying and pickling foods. Contact your local Extension office for more information about safely preserving a variety of foods.